Bonding pads (often referred to as "bondpads") in microelectronic devices such as integrated circuits are commonly used during electric die sort (EDS) tests and other testing and fabrication processes. A typical bonding pad includes a plurality of metal wiring layers, connected to each other by a contact plug. The bonding pad typically has relatively low conductivity because the contact plug that connects the metal wiring layers is typically made of tungsten.
When a probe tip is connected to a bonding pad during a process such as EDS, physical force may be applied to the bonding pad to the point that damage to the bonding pad structure may occur. Similarly, wire bonding processes may apply sufficient force to the bonding pad such that the structure of the bonding pad is damaged. For example, a phenomenon called chip out under bondpad (COUB) may occur, wherein a lower portion of the bonding pad is broken. The occurrence of COUB can be determined by performing a bond pull test (BPT), wherein a wire bonded to the bonding pad is pulled upward by a predetermined force that is small enough such that an undamaged bonding pad will not pull free, but large enough such that a damaged bond pad will break free at its lower portions.
A device having a COUB defect can have several problems. First, a wire connected to a bonding pad suffering from COUB may be easily detached. Second, current may leak at the area where COUB occurs, potentially deteriorating electrical characteristics of the device. Third, the overall durability of the device may be reduced, which in turn may reduce the reliability of electronic equipment in which the device is used.